Schema:
Ref_Characteristic_Types (characteristic_type_code, characteristic_type_description)
Ref_Colors (color_code, color_description)
Ref_Product_Categories (product_category_code, product_category_description, unit_of_measure)
Characteristics (characteristic_id, characteristic_type_code, characteristic_data_type, characteristic_name, other_characteristic_details)
Products (product_id, color_code, product_category_code, product_name, typical_buying_price, typical_selling_price, product_description, other_product_details)
Product_Characteristics (product_id, characteristic_id, product_characteristic_value)
Please answer with SQL.